Squid Reproduction: Don’t Mess with Squid Eggs!

SOMETIMES, DURING DIVES, YOU ENCOUNTER THESE THINGS attached to the bottom. They’re squid eggs. Here’s a hint: Don’t Mess With Them!

Remember Kirk Douglas battling the giant squid in 20,000 Leagues Under the Sea? It’s could be like that. Maybe.

MAKING MORE SQUIDS

Squid reproduction is a complex process that involves fertilization following the transfer of a male squid’s sperm – in the form of a single bundle called a spermataphore – into a female’s central mantle cavity for fertilization. In many shallow water species, the gonoduct for doing so is short and the male uses a specially adapted arm to place the spermatophore within the cavity. Within a female, special glands assist in nutrient manufacture and shell formation for the newly fertilized eggs.

The females then plant them in clusters, consisting of two-inch-long, finger-shaped gelatinous capsules, deposited on the seafloor or attached to algae or other features. Squid egg masses are communal, meaning that more than one squid will contribute eggs. Each capsule holds up to 200 eggs.

Being a squid makes for a tricky life. They’re favorite prey for many ocean denizens – sharks, bony fish like jacks, whales, dolphins, eels and sea snakes. And, of course, humans. Their eggs are attractive as food for fish and other predators, as well. To ensure species survival, they produce them in the thousands.

DESIGNED TO DRIVE GUYS MAD!

When a female squid deposits her capsules on the seafloor, she also imbues them with a protein that essentially drives male squids crazy – not about her but about the eggs.

Studying longfin squid reproduction (Loligo pealeii), researchers discovered that the outer tunics of squid eggs are embedded with a protein called Loligo microseminoprotein.

DON’T TOUCH!

Male squids are drawn to the eggs visually, but touching them – and the protein – has the effect of transforming them into lean, mean fighting machines, ready to take on any other male squids who might get near the eggs. [Editor’s note: I’ve been told anecdotally that squids can become aggressive towards divers who touch the eggs.]

Similar proteins are found in other animals, including mammals, although their function is not clear. This is the first substance found in marine creatures shown to trigger aggression.

EXCEPTIONS TO THE RULE:

In contrast to the at least one species of squids brood its eggs. A species called Gonatus onyx spends most of its time in shallow waters, but descends to depths of some 8,000 ft/2,500 m to lay some 2,000 to 3,000 eggs. Instead of anchoring them to the bottom, however, G. onyx carries their eggs around in a mass. For up to nine months.

While hauling a mass of eggs around for an extended period is laborious, it seem likely that doing so in the depths represents a strategy for minimizing exposure to predators.